There were a few trips where I had considered staying a few extra days but I wasn't sure if it would be a process I would regret. I would have to rebook with the same hotel or find another one and I didn't want to risk being without a room or something. Has anyone ever done this before?
I have once as it was offered to me for a discount. It was at the hotel I was already staying in. This was during their slow period so I took the deal. I have no experience with having to rebook outside of this though.
It can be a complicated pain in the behind but this is only the case if they are super busy. Most hotels have extra rooms. You can easily get switched to a different room and often at a discount. It is worth inquiring about before your trip has ended just in case you decide to stay.